System Diagnosis - Secondary Ignition

When any condition is suspected to be caused by or related to the ignition control system, the first step in diagnosis should be to check for stored PCM DTCs. Diagnose all DTCs before further action is taken. If no DTCs are stored and the condition is still present, refer to the following:

^ Ignition System Check

^ Symptoms


Circuit Description
The Secondary Ignition Check tests for faulty spark plugs, plug wires, or Ignition Control (IC) Module/Coils. This table requires the J 26792 spark tester (ST-125).


Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.

7. Ensure good DVM contact when measuring spark plug resistance.When manufactured,the normal resistance for the spark plug is 900-2500 ohms but resistance growth up to 10K ohms is considered normal.

8. J 26792 spark tester (ST 125) presents a more difficult load on the secondary ignition than a normal spark plug. If a miss, stumble, or hesitation is being caused by a spark plug not firing, the spark tester should also not fire.

10. The companion spark plug shares the same ignition coil with the spark being tested (1-4, 2-5, 6-7, 3-8).

11. If the no spark condition follows the suspected coil, that coil is faulty. Otherwise, the ignition module is the cause of no spark. This test could also be performed by substituting a known good coil for the one causing the no spark condition.

16. Ensure good DVM contact when measuring spark plug resistance. When manufactured the normal resistance for the spark plug is 900-2500 ohms but resistance growth up to 10K ohms is considered normal. A suspected ignition system miss may actually be a fuel system problem. Perform the Fuel System Check, if it has not yet been performed.

18. If the no spark condition follows the suspected coil, that coil is faulty. This test could also be performed by substituting a known good coil for the one causing the no spark condition.